In recent years, with an increase of interest in the global environmental, environmental measures have been emphasized in cement production equipment which uses industrial waste effectively, final disposal site of industrial waste, petrochemical plants, and various factories. For example, various methods and devices, which purify gas or waste water discharged from cement production equipment, final disposal site of industrial waste, factories, etc., are suggested and used in practice.
For example, a chlorine bypass device is installed in cement production equipment in order to remove volatile components such as chlorine contained in industrial waste.
The chlorine bypass device is a device for removing volatile components such as chlorine which is concentrated by repeating volatilization and condensation between a cement kiln and a preheater. In this chlorine bypass device, chlorine is removed from the cement kiln by bleeding exhaust gas from the bottom of a cement kiln, and cooling to form chlorine bypass dust in which volatile components containing a chlorine compound as a main component are solidified, and discharging the chlorine bypass dust.
Since the chlorine bypass dust which is produced in the chlorine bypass device contains many chlorine compounds and heavy metals. Therefore, when the chlorine bypass dust is reused as a cement raw material, the contained chlorine compounds, heavy metals, etc have to be removed.
As a disposal method for separating and recovering chlorine compounds from waste containing chlorine, for example, a method, which has a rinse step for rinsing the waste containing chlorine with water to perform solid-liquid separation, that is, elute a chlorine component and a lead component, an alkali elution step for eluting the lead component by adding an alkali solution in the filtered solid component together with filtering and separating calcium as a hydroxide, a lead removal step for adding the filtrate separated in the alkali elution step to the filtrate separated in the rinse step, and adding an sulfating agent to participate and remove lead, a calcium removal step for adding a carbonated source to the free lead filtrate to participate and remove calcium, and a salts recovery step for crystallizing chlorides by heating the filtrate to participate and recover chlorides, is suggested (Patent Document No. 1).
On the other hand, there is a possibility that environmental pollution such as soil pollution, may arise by the waste water containing heavy metals such as lead, cadmium, and chromium at the final disposal site of industrial waste and some factories.
There is a possibility that the waste water containing heavy metals not only worsens the water quality of a river, but also causes air pollution, soil pollution, etc. Therefore, it is necessary to remove heavy metals contained in waste water as much as possible to improve the water quality.
The waste water containing heavy metals also contains inorganic salts, organic halogenated compounds such as dioxin, endocrine disruptors which are called as environmental hormones, and persistent substances such as plastic material. Therefore, it is necessary to remove these substances to improve the water quality.
Also, a disposal apparatus for waste water containing heavy metals which has a heavy metal absorbing device for absorbing and removing heavy metal ions contained in the waste water using an iron based adsorbent, a deionization device for further removing the heavy metal ions remaining in the waste water from the heavy metal absorbing device, and a circulation means for returning the concentrated water discharged from the deionization device to the heavy metal absorbing device is suggested (Patent document No. 2).
In addition, a waste water disposal device which has a settler for adjusting pH and settling metals contained in the waste water as metal hydroxides using a non-ionic polymer aggregating agent, a neutralization tank for neutralizing the treated wastewater after settle of metal hydroxides, an electrolysis device for condensing the salts in the treated water by passing the neutralized treated water, and an evaporator for evaporating moisture component from the water obtained after concentration treatment for the salts to crystallize salts contained in the treated water is also suggested (Patent document 3).    [Patent document No. 1] Japanese Unexamined Patent Application, First Publication No. 2003-1218    [Patent document No. 2] Japanese Unexamined Patent Application, First Publication No. 2005-103518    [Patent document No. 3] Japanese Unexamined Patent Application, First Publication No. 2005-161188